The method of the invention will in particular be suitable for determining the suitability of yarns for weaving and knitting purposes. It is however envisaged that the method of the invention could find other applications and the term "yarn" herein includes any elongated fibre, strand, string, sliver or the like. The method of the invention envisages determining the tensile properties of a yarn and could also give a satistical indication of the number of weak points per unit length of yarn.